Method and apparatus for terminating transmission of a message in an enhanced random access channel

ABSTRACT

A method and an apparatus is provided for terminating an enhanced random access channel (E-RACH) message in an E-RACH transmission. Triggers for terminating the E-RACH message are provided. The actions upon termination of the E-RACH messages are provided to release enhanced dedicated channel (E-DCH) resources while in cell forward access channel (CELL_FACH) state or transition to cell dedicated channel (CELL_DCH) state.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/319,608, filed Jun. 30, 2014, which is a continuation of U.S. patentapplication Ser. No. 12/238,910 filed Sep. 26, 2008, now known as U.S.Pat. No. 8,774,104, which issued on Jul. 8, 2014, and claims the benefitof U.S. Provisional Application No. 60/975,985 filed on Sep. 28, 2007;U.S. Provisional Application No. 60/982,528 filed on Oct. 25, 2007; U.S.Provisional Application No. 61/018,999, filed on Jan. 4, 2008; U.S.Provisional Application No. 61/025,441 filed on Feb. 1, 2008; U.S.Provisional Application No. 61/038,576 filed on Mar. 21, 2008; U.S.Provisional Application No. 61/074,288 filed on Jun. 20, 2008; and U.S.Provisional Application No. 61/083,409 filed on Jul. 24, 2008, which areincorporated by reference as if fully set forth. U.S. patent applicationSer. No. 14/319,608 is also related to U.S. patent application Ser. No.14/319,975 filed on Jun. 30, 2014, and is incorporated by reference asif fully set forth.

FIELD OF INVENTION

The present application is related to wireless communication.

BACKGROUND

In wireless communications systems, access to radio resources iscontrolled by a radio network. When a wireless transmit receive unit(WTRU) has data to transmit to the network, the WTRU requires access tothe radio resources before transmitting its data payload. In a ThirdGeneration Partnership Project (3GPP) network, the WTRU may transmit onthe uplink using a contentious channel known as a random access channel(RACH). Because access to the RACH is contentious, a collision mightoccur when multiple WTRUs are accessing the resources simultaneously.

The current RACH access procedure in the 3GPP comprises a preamble phasewith power ramp-up, followed by channel acquisition information andmessage transmission for random access. Because the RACH is a sharedchannel, in order to avoid WTRUs holding the shared radio resource for along time, only relatively short message payloads are transmitted on theRACH; this leads to a relatively small data rate. The RACH is thus usedfor the transmission of short control messages. Typically, the WTRUsdemanding larger data rates may be configured by the network to usededicated resources.

The data rate provided by the RACH is sufficient for the transmission ofshort control messages supporting mostly speech communications, howeverit may be inefficient for transmission of data messages associated tothe new non real-time data services such as internet browsing, e-mail,etc. For such data services, the traffic is ruptured by nature and longperiods of inactivity may exist between successive transmissions. Forexample, applications requiring frequent transmission of keep-alivemessages, may result in an inefficient utilization of dedicatedresources. In such cases, it may be advantageous for the network to useshared resources for data transmission instead. The difficulty however,resides in the low data rate offered by the RACH.

To overcome these difficulties, it was proposed to use the enhanceddedicated channel (E-DCH) in the CELL_FACH state to increase the datarate of the shared channel.

FIG. 1 is a diagram of an enhanced RACH (E-RACH) access. The E-RACHprocedure may include, a RACH preamble phase and an E-RACH messagephase. During the initial RACH preamble phase, a WTRU transmits a RACHpreamble, it continues transmitting the preamble while ramping up thepower of the transmission until it receives an initial resourceassignment. The WTRU may also perform collision detection andresolution, if other WTRUs are attempting to access the RACH during thistime. Once the WTRU has received permission to access the RACH, the WTRUmay transmit data until the resources are released or the WTRUtransitions to another state.

As mentioned above, it was proposed to use the E-DCH in a CELL_FACHstate to increase the data rate of the shared channel. However, in thecurrent standard, there are no methods to terminate the E-RACH messagephase. Accordingly, it would be beneficial to provide a method andapparatus to terminate an E-RACH message phase in an E-RACH.

SUMMARY

A method and an apparatus is provided for terminating an E-RACH messagein an E-RACH transmission. Triggers for terminating the E-RACH messageare also provided. The actions upon termination of the E-RACH messagesor transition to CELL_DCH state are provided in order to release theshared E-DCH resources while in the CELL_FACH state.

A method for terminating an enhanced random access channel (E-RACH)message in an E-RACH transmission determining that a buffer is empty;triggering a transmission of a scheduling information (SI) with thevalue of total enhanced dedicated channel (E-DCH) buffer status (TEBS)equal to zero; determining last hybrid automatic repeat request (HARQ)data transmission; and releasing the E-DCH resources allocation isprovided.

A method for terminating an enhanced random access channel (E-RACH)message in an E-RACH transmission where the network waits until a HARQbuffer is empty and when the SI with a value of zero is received, theresources are released.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example and to be understood in conjunction with theaccompanying drawings wherein:

FIG. 1 is a diagram of an E-RACH access with an E-DCH;

FIG. 2 shows a wireless communication system;

FIG. 3 is a functional block diagram of a WTRU and the base station ofthe wireless communication system shown in FIG. 2;

FIG. 4 is a flow diagram of a E-DCH resource allocation andde-allocation;

FIG. 5 is a diagram of triggers for starting the timer that the WTRU mayinitiate for the timers;

FIG. 6 is a flow diagram of a method to release E-DCH resources based onthe status of a WTRU's queue or buffer;

FIG. 7 is a flow diagram of a network configured to determinetermination of an E-RACH message transmission;

FIG. 8 is a flow diagram of E-DCH resources release when the WTRUtransitions from the CELL_FACH state to the CELL_DCH state; and

FIG. 9 is a flow diagram for releasing the E-DCH resources while in theCELL_FACH state.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the terminology “base station” includes but isnot limited to a Node-B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

When referred to herein, the term RACH and E-RACH may be used todescribe a resource that is selected by a WTRU for uplink contentionbased access. The term E-RACH resource may also indicate any combinationof a scrambling code, a channelization code, a timeslot, an accessopportunity, or a signature sequence that are associated to an E-RACHchannel in a future system architecture. The term E-RACH may alsoindicate the use of the E-DCH in CELL_FACH, CELL_PCH, URA_PCH states orIdle mode.

When referred to hereafter, the term enhanced medium access control(MAC)-e/es entities may refer to the MAC entities used to perform E-DCHtransmission in the CELL_FACH state, which in release 8 is referred toas MAC-i/is. MAC-e/es and MAC-i/is are the MAC entities that handle thetransport channel such as the enhanced dedicated transport channel(E-DCH).

FIG. 2 shows a wireless communication system 200 including a pluralityof WTRUs 210, a base station 220, a CRNC 230, an SRNC 240, and a corenetwork 250. As shown in FIG. 2, the WTRUs 210 are in communication withthe base station 220, which is in communication with the CRNC 230 andthe SRNC 240. Although three WTRUs 210, one base station 220, one CRNC230, and one SRNC 240 are shown in FIG. 3, it should be noted that anycombination of wireless and wired devices may be included in thewireless communication system 200.

FIG. 3 is a functional block diagram 300 of a WTRU 210 and the basestation 220 of the wireless communication system 200 of FIG. 2. As shownin FIG. 3, the WTRU 210 is in communication with the base station 220and both are configured to perform a method to terminate transmission ofa message in an E-RACH.

In addition to the components that may be found in a typical WTRU, theWTRU 210 includes a processor 215, a receiver 216, a transmitter 217,and an antenna 218. The processor 215 is configured to perform a methodto terminate transmission of a message in an E-RACH. The receiver 216and the transmitter 217 are in communication with the processor 215. Theantenna 218 is in communication with both the receiver 216 and thetransmitter 217 to facilitate the transmission and reception of wirelessdata.

In addition to the components that may be found in a typical basestation, the base station 220 includes a processor 225, a receiver 226,a transmitter 227, and an antenna 228. The processor 225 is configuredto perform a method to terminate transmission of a message in an E-RACH.The receiver 226 and the transmitter 227 are in communication with theprocessor 225. The antenna 228 is in communication with both thereceiver 226 and the transmitter 227 to facilitate the transmission andreception of wireless data.

FIG. 4 is a flow diagram of E-DCH resource allocation and de-allocation400 using triggering for a WTRU. The first state corresponds to a WTRU210 that operates with no E-DCH resources allocated to it 405. Onceuplink (UL) data has to be transmitted, the WTRU 210 requests E-DCHresources from the network, by transmitting a preamble and waiting forthe response on the acquisition indication channel (AICH). In otherwords, the WTRU 210 may remain in this state until it receives apositive acknowledgement (ACK) on the AICH, or a negativeacknowledgement (NACK) on the AICH followed by a resource assignmentindex over the E-AICH, which may also be referred to as the WTRU 210receiving an E-DCH index. After receiving the E-DCH resource assignment,the WTRU may transition to the next state wherein E-DCH resources areallocated for enhanced uplink transmissions 410. The WTRU 210 may usethese E-DCH resources for UL transmission until it receives a trigger,at which point the WTRU 210 will release the resources 415. After theWTRU 210 releases the resources, it returns to the initial state. Aswill be described in further detail hereafter, the trigger may be timerbased, it may be based on the WTRU buffer status, or may be based onsignaling from the RNC or the Node-B 220.

In one embodiment, the WTRU 210 may be configured to include a timermodule. The timer module may include multiple timers, wherein a timermay be associated to each logical channel or each MAC-d flow. The timermodule may be configured to indicate the maximum allowable transmissiontime for a logical channel (i.e., dedicated control channel (DCCH),dedicated traffic channel (DTCH), common control channel (CCCH), etc.).The values for the timer module may be preconfigured or signaled to theWTRU 210. The timers may be activated upon the WTRU's 210 firsttransmission, once an E-DCH resource index is received. The WTRU may beconfigured to release an E-DCH resource upon expiry of its associatedtimer. For example, the WTRU 210 may be configured to release a commonE-DCH resource when the maximum common E-DCH resource allocation timefor the CCCH has been reached. This embodiment would allow theflexibility to configure a smaller transmission time duration for alogical channel such as the CCCH.

The timer module may also be configured based on logical channelidentity and the absence of an E-DCH radio network temporary identifier(E-RNTI). More specifically, a maximum E-DCH allocation time may beallocated to the CCCH transmission when an E-RNTI is not present. If thetimer expires, and the WTRU 210 that is performing a CCCH transmissiondoes not have the E-RNTI present, the E-RACH access is terminated andthe resources are released. If a CCCH transmission is occurring and anE-RNTI is present, (which may occur during period cell update procedure)then the WTRU 210 is not configured to have a maximum E-DCH allocationtime and the timer will not affect the WTRU 210.

Alternatively, the network may configure the transmission duration timerbased on the presence or absence of an E-RNTI. The WTRU 210 may beconfigured to have a maximum E-DCH allocation time if it has data (userplane or control plane) to transmit and no E-RNTI is present. Otherwiseif an E-RNTI is present the WTRU 210 is not configured with a maximumE-DCH allocation time.

FIG. 5 shows a diagram of triggers for starting the timer that the WTRU210 may initiate for the timers T₁ and T₂ 500. The timers such ascollision resolution T₁ and CCCH timer T₂ are started according to oneof the triggers 501 to 505. This embodiment may include any combinationof at least one of the shown trigger 501-505 for starting the timer 506.The timer may start if an ACK associated to the preamble signaturetransmitted is received on the AICH or E-AICH 501. The timer may startas soon as the radio resource control (RRC) provides the MAC with thetimer values, and after receiving the E-DCH resource index 502. Thetimer may start if the WTRU 210 starts the first dedicated physicalcontrol channel (DPCCH) preamble transmission 503. The timer may startwhen the initial DPCCH transmission is completed after E-DCHtransmission backoff transmission time intervals (TTIs) or the first MACprotocol data unit (PDU) is passed to the physical layer 504. Or, thetimer may start when the WTRU 210 starts the E-DCH transmission 505. Inaddition, the WTRU 210 may initiate the timer when the collisionresolution E-DCH absolute grant channel (E-AGCH) carrying the WTRU 210E-RNTI is received. Other triggers may also be used as designed.

Alternatively, the WTRU 210 timer module may be configured such that thelength of time available to the WTRU 210 is based on the number of databits that need to be transmitted. The length of the time variable to theWTRU 210 may also be based on the number of radio link controller (RLC)or MAC PDUs. Additionally, it may also be based on the number of RLCservice data units (SDUs).

Alternatively, the E-RACH message duration may be fixed at either 10msec or 20 msec (as is specified in the current 3GPP standards). As aresult, the E-RACH message phase may be active for a maximum number offrames or sub-frames. An E-RACH message duration information element(IE) may be broadcast as part of the system information broadcast (SIB),or may be included as part of L1 signaling. For example, the E-RACHmessage duration IE may be transmitted with the initial resourceassignment or during the collision resolution phase. In addition, theE-RACH message duration may be linked to an access service class.

Alternatively, the WTRU 210 may count the number of transmissions andretransmissions and use the count as a trigger to stop the transmissionof the E-RACH message phase. For example, if the WTRU 210 is configuredfor repeat automatic repeat request (ARQ) type of operation andtransmission on consecutive TTIs, then the WTRU may be configured toterminate the transmission of the E-RACH message phase after Kretransmissions. It is noted that the value of K may be preconfigured inthe WTRU, broadcasted as part of the SIB, or signaled during the E-RACHallocation phase.

FIG. 6 is a flow diagram of a method to release E-DCH resources based onthe status of a WTRU's 210 queue or buffer. When the WTRU 210 has datain the transmit buffer, the WTRU 210 may transmit the data 605. After atransmission, the WTRUs 210 may check if the transmit buffer is empty610. If the transmit buffer is not empty, then the WTRU 210 willtransmit the data that is in the buffer 605. If the transmit buffer isempty 610 (i.e., the Total E-DCH Buffer Status (TEBS) is equal to zero),optionally it is checked if an inactivity timer has expired 615. If theinactivity timer has expired, then the WTRU 210 may be configured totransmit a special or reserved value of the SI where TEBS is set to zero620. The WTRU 210 may be configured to release E-DCH resource 630 afterthe inactivity timer has expired 615, wherein the inactivity timer isstarted once the TEBS is equal to zero. The WTRU 210 is considered to beinactive, if no UL or downlink (DL) traffic has been received.Alternatively, the implicit release timers (i.e., the inactivity timer)may be restarted based on a trigger mechanism when the WTRU 210 decodesits H-RNTI on the high speed shared control channel (HS-SCCH). Once theinactivity timer has expired, the WTRU 210 may be configured to transmita special or reserved value of the SI 620. For example, the special orreserved value of the SI may comprise a TEBS with a value set to zero620. The SI with the TEBS set to zero may be used to signal to thenetwork for releasing the resources. After successfully transmitting theSI and emptying the HARQ buffers 625, the WTRU 210 releases the E-DCHresources 630.

Alternatively, the WTRU 210 may transmit a signal to the networkindicating to release the resources. The signal may comprise a specialcombination of the SI and a Happy Bit, a new MAC signaling, where aspecial combination of MAC header fields may be re-interpreted.Alternatively, a field may be added in the enhanced MAC-e header orMAC-e trailer denoting a request to terminate transmission of the E-RACHmessage phase. For example, the WTRU 210 may transmit this signal to thenetwork via a reserved data description indicator (DDI) combination. Inanother alternative, the signal may be a new RRC message; special valueof the enhanced transport format combination index (E-TFCI) field in theE-DPCCH or a special combination of the E-DPCCH fields; or, a new L1message. The final decision to release the resources may be determinedby the network; which may indicate the release of resources back to theWTRU 210. Alternatively, the WTRU 210 may simply stop transmission ofthe E-DCH as a means to indicate the termination of the E-RACH messagephase, at which point the network may release the radio resources.

Alternatively, the timer module may be configured to start when the WTRU210 has transmitted all PDUs which were present when the E-RACH wasinitiated, or the buffer has passed a predetermined threshold level. Thethreshold level may be an absolute value or based on a relative measureusing the initial queue size.

Releasing the resources upon the transmission of all PDUs in the bufferthat pass a predetermined threshold level, may free up the E-RACHresources for other WTRUs 210. For example, the threshold levels may beset to allow the network to tradeoff fairness between WTRUs 210 andtransmission delay. These levels may be configured through systeminformation or they may be preconfigured in the WTRU 210.

In addition, there may be procedures for physical layer that may triggera termination of the E-RACH message transmission. This includes cellreselection and measurements controlled by the FACH measurementoccasions or detection of radio link (RL) failure.

Alternatively, the WTRU 210 may suspend all transmission during themeasurement occasion. Also, the scheduler at the Node-B 220 may be awareof the measurement occasion and may also suspend any grant, ACK, or NACKdownlink transmission. Upon resuming normal operation, the network mayoptionally transmit an initial grant so that the power control loop maybe re-established. Or, the network may wait for an indication from theWTRU 210 using a preamble power ramp or similar procedure. Optionally,the WTRU 210 may indicate the reason for termination in the terminationsignal or the termination message. Reasons for E-RACH termination mayinclude a RL failure and E-RACH transmission complete.

FIG. 7 shows a flow diagram of a network configured to determinetermination of an E-RACH message transmission 700. The termination ofthe E-RACH message phase may be established by the network based on thereception of the amount of data indicated in an initial SI 705 by theUniversal Mobile Telecommunications System (UMTS) Terrestrial RadioAccess Network (UTRAN). Alternatively, it may be established based onthe UTRAN receiving the amount of data indicated in subsequent SIs orindicated using a different mechanism. The UTRAN may use the values ofSI to determine when to terminate the message transmission. Morespecifically, an SI with TEBS set to zero 710 signals to the networkthat the WTRU 210 is releasing the resources once the transmission ofdata in the HARQ buffers is completed. The UTRAN releases E-DCHresources 720 after SI with TEBS set to zero is received and there is nomore HARQ transmission 715.

Alternatively, the UTRAN may simply turn off transmission of theassociated F-DPCH and explicit additional signaling is not used. Thisapproach may be used in the case where both the WTRU 210 and the networkare aware that the transmission is to be terminated.

Alternatively, SI may be transmitted every time the buffer occupancychanges. Alternatively, an SI may be transmitted every time the bufferoccupancy changes by a pre-defined or signaled amount (i.e., additionaldata is received in the buffer), even if the new data is not from higherpriority logical channels. If the TEBS is equal to zero then the SItriggering mechanism may be modified to allow the SI to be transmitted.The SI with TEBS set to zero signals to the network that the WTRU isreleasing the resources once the transmission of data in the HARQbuffers is completed and the UTRAN also releases the E-DCH resources.Alternatively, an SI may be transmitted in every HARQ transmission whenthe WTRU 210 is in CELL_FACH state or occupying E-RACH resources.

In another termination option, the UTRAN may explicitly signal the endof the E-RACH transmission. Once the UTRAN determines the end of theE-RACH message transmission, it signals to the WTRU 210 by transmittinga special value over the E-AGCH (e.g., a 0 grant). Or, the UTRAN signalsto the WTRU 210 by transmitting an RRC message over the FACH or over theHigh Speed Downlink Shared channel (HS-DSCH) if the WTRU 210 isconfigured for HS-DSCH in CELL_FACH state. Alternatively, the networksignals to the WTRU 210 by using L1 signaling. This may include stoppingthe fractional dedicated physical channel (F-DPCH) or transmitting aflag or combination of pre-determined fields on the HS-SCCH if the WTRU210 is configured for HS-DSCH in CELL_FACH state, for example, using anHS-SCCH order.

Alternatively, the termination of the E-RACH message may be establishedbased on a lack of activity on the enhanced dedicated physical datachannel (E-DPDCH) or enhanced DPCCH (E-DPCCH) transmission.

The termination of the E-RACH part may also be established based on thestatus of the WTRU 210 scheduling requests. As an example, the UTRAN maymonitor the received SI or Happy Bit status. If this informationindicates low usage, the network may decide to terminate the currenttransmission of the E-RACH message so that the other WTRUs 210 may havean opportunity to access the resources. Alternatively, if thisinformation indicates high usage and continued need with the Happy Bitset to unhappy, then the UTRAN may decide to transition the WTRU 210 toCELL_DCH state. As another alternative, the UTRAN may use the trafficvolume measurement report (such as uplink RRC measurement report) todetermine that the WTRU 210 does not have any further data or a smallamount of data to transmit.

Alternatively, the UTRAN may implicitly signal the WTRU 210 to releasethe E-RACH resource by not transmitting predefined physical channels orsignals for a predetermined amount of time. In other words, the WTRU 210releases the E-RACH resources if it does not receive any transmissionfrom the UTRAN on either channel E-AGCH destined to the WTRU 210, E-RGCHassociated with E-RACH resource that is used by the WTRU 210, F-DPCHassociated with the E-RACH resource that is used by the WTRU 210,and/or, HS-SCCH or high speed physical downlink shared channel(HS-PDSCH) that is destined to the WTRU 210.

Optionally, the UTRAN may indicate the reason for termination in thetermination signal or termination message. Reasons for E-RACHtermination may include, but are not limited to an RL failure,completion of the E-RACH transmission, and network congestion.

FIG. 8 is a flow diagram of the E-DCH resources released when the WTRU210 transitions from the CELL_FACH state to the CELL_DCH state. The WTRU210 operates without any E-DCH resources allocated 805. Upon receivingan E-DCH resource assignment on the AICH or E-AICH or a NACK on the AICHfollowed by a resource assignment index over the E-AICH, which may alsobe referred to as the WTRU 210 receiving an E-DCH index, the WTRU 210may access the E-DCH resources allocated to it in the CELL_FACH state810. The WTRU 210 retains control of the E-DCH resources until itreceives a reconfiguration message, (e.g., via the FACH or the HS-DSCH),indicating that a switch to the CELL_DCH state may be performed. TheE-DCH resources are then released 815. And, the WTRU 210 may transitionto the CELL_DCH state 820. If the UTRAN reconfigures the WTRU 210 to theCELL_DCH state with dedicated E-DCH resources while the WTRU 210 istransmitting over the E-RACH, then the WTRU 210 may release the E-RACHresources at the activation time that is specified in thereconfiguration message in the case of synchronous reconfiguration.Alternatively, the WTRU 210 may release the E-RACH resources at a fixeddelay prior to or after the activation time. Alternatively, the WTRU 210may release the E-RACH resources immediately upon reception of the RRCreconfiguration message.

Additionally, the WTRU 210 may be configured to release the E-RACHresources at the same time as it configures itself for a transmissionover the dedicated E-DCH resources. Alternatively, the WTRU 210 mayrelease the E-RACH resources at a fixed delay prior to or afterconfiguring itself for transmission using the dedicated E-DCH resources;or, release the E-RACH resources once the WTRU 210 is fully synchronizedwith the UTRAN with the dedicated E-DCH resources.

FIG. 9 is a flow chart of a procedure for releasing the E-DCH resourceswhile in the CELL_FACH state or idle mode, when the E-RACH terminationtriggers occur. The WTRU 210 begins the E-RACH termination process 905.The WTRU 210 may be configured to stop any E-AGCH, E-RGCH, and E-HICHreception procedures that are occurring 910. The WTRU 210 may be furtherconfigured to stop any E-DPCCH and E-DPDCH transmission procedures thatare occurring 915. The WTRU 210 may then perform a MAC reset procedure920 and release HARQ buffers 930. The enhanced MAC-e/es reset proceduremay include flushing the HARQ processes, discarding any remainingsegments in the segmentation entity of the enhanced MAC-e/es andresetting the CURRENT_transmission sequence number (TSN) value to zero.Alternatively, if the remaining segment is from a DTCH or a DCCH logicalchannel the WTRU 210 may resume transmission of the segment at aremaining process. An indication may be transmitted to the SRNC 240 viaIub signaling to discard any stored segment and reset the TSN reorderingnumbers.

If the E-DCH has terminated and the DTCH or the DCCH transmission isactive, the WTRU 210 may flush the HARQ processes 930 and discard anyremaining segments in the segmentation entity of the MAC-i/is.

The other logical channels or queues of the MAC-i/is entity that do notcorrespond to the CCCH are not reset. The Node-B 220 may be configuredto perform a reset of the MAC-is entity of the CCCH. In other words, anysegment may be discarded and the expected TSN is set to its initialvalue. If the MAC-is entity is in the CRNC 230, Node-B 220 uses Iubsignaling indicating to the MAC-is entity to perform a reset. Inaddition, the MAC-i entity associated to the E-DCH resource is reset(i.e., HARQ soft buffers are flushed).

When the WTRU 210 performs a full MAC-i/is reset, the MAC-is entity inthe SRNC 240 may be notified via a new Iub/Iur signaling that E-RACHaccess has been terminated; thus MAC-is entity in the SRNC 240 may alsoperform a reset. More specifically, when the Node-B 220 terminates theE-DCH connection with the WTRU 210, it releases the E-DCH resources,flushes the HARQ buffers, and notifies the SRNC 240 or CRNC 230 that theconnection has been terminated and thus the CRNC 230 or SRNC 240 alsoperform a reset of the MAC. The CRNC 230 or SRNC 240 is notified via Iubor Iur signaling. A new control bit may be introduced in the Iub or Iurframe format or a new frame format may be defined to signal to the SRNC240 or CRNC 230 the release of the resources.

Also, optionally, the reset of the MAC-i/is or only discarding of thesegments may be performed after a time interval (Tr) because thetermination of the E-RACH resource. The timer is also initiated in thenetwork side. Tr may be a system configured timer signaled to the WTRU210 via RRC message, via system information block (SIB), orpreconfigured in the WTRU 210. The timer is initiated as soon as theE-DCH resources are terminated in the WTRU 210.

The WTRU 210 may be configured to stop the timer if it is running and ifthe WTRU 210 attempts to perform E-RACH access. Also, the WTRU 210 mayalso stop the timer, if the WTRU 210 attempts the E-RACH access andobtains the E-DCH resources assigned, or the WTRU 210 obtains the E-DCHresources assigned and resolves the contention resolution phase.

Alternatively, the WTRU 210, the Node-B 220 and/or the RNCs may beconfigured with a TSN_RESET_TIMER, wherein the WTRU 210 is configured toperform a TSN reset when the timer expires. Optionally, the WTRU 210 mayperform a full enhanced MAC-e/es reset procedure when the timer expires.

The E-DCH resources are released when a transition from CELL_FACH toCELL_DCH occurs.

The WTRU 210 and the RNC may reset the value of the last used TSN number(i.e., CURRENT_TSN) to the initial value upon the release of the E-DCHresource set being used by the WTRU 210. The WTRU 210 and the RNC mayeach include synchronized timers, wherein the expiry of the timersignals the release of the E-DCH resources. After the timer expires andthe resources are released, the WTRU 210 may reset the TSN andoptionally perform a full enhanced MAC-e/es reset procedure.

Alternatively, the UTRAN may order the release of the resources. TheUTRAN may signal the WTRU indicating that the resources must bereleased. In this case, upon reception of the message, the WTRU 210 andUTRAN reset the TSN to an initial value.

Alternatively, the TSN number may be reset upon the expiration of aninactivity timer. In this case, an inactivity timer may be started inboth the WTRU 210 and the network after the last MAC-e PDU istransmitted and received, respectively. If the timer expires, the WTRU210 and the RNC resets the TSN to its initial value. Optionally, a fullenhanced MAC-e/es reset procedure may be performed.

In another alternative, the TSN number may not reset. The last TSNvalues used are stored in memory and continuously incremented for eachnew transmission, regardless of the E-DCH resource set being used or thetime in which the transmission is taking place.

Alternatively, the TSN number may be set to its initial value andoptionally a full enhanced MAC-e/es reset may take place when a cellreselection occurs. Resetting the TSN or the MAC-e/es may always occurafter the WTRU 210 performs cell reselection. Alternatively, it may onlyoccur when a serving radio network subsystem (SRNS) relocation occurs.The RNC may signal the TSN reset via an explicit enhanced MAC-e/es resetindicator or the WTRU 210 may implicitly detect that SRNS relocation hasoccurred due to the presence or the change of a new UTRAN RNTI (U-RNTI).

Although features and elements are described above in particularcombinations, each feature or element may be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmware tangiblyembodied in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU)comprising: a receiver; a transmitter; and a processor, wherein theprocessor: causes the transmitter to transmit to a network node a randomaccess procedure preamble sequence; processes one or more signalsreceived by the receiver from the network node, the one or more signalsbeing responsive to the transmitted random access procedure preamblesequence, the one or more signals identifying resources allocated forretransmission of a random access message by the WTRU and indicating anumber of times that the WTRU is to retransmit the random accessmessage, wherein the random access message is different from the randomaccess procedure preamble sequence; and causes the transmitter toretransmit to the network node the random access message the number oftimes using the allocated resources, wherein the random access messageis retransmitted using a hybrid automatic repeat request entity.
 2. TheWTRU of claim 1, wherein the random access message is used for collisionresolution.
 3. The WTRU of claim 1, wherein the random access message isretransmitted using a shared channel.
 4. A method of operating awireless network, the method comprising: operating a base station withinthe wireless network to: process a random access procedure preamblesequence received from a wireless transmit/receive unit (WTRU); andtransmit to the WTRU, responsive to the received random access procedurepreamble sequence, one or more signals identifying resources allocatedfor retransmission of a random access message by the WTRU to the basestation and indicating a number of times that the WTRU is to retransmitthe random access message to the base station, wherein the random accessmessage is different from the random access procedure preamble sequence,wherein the base station is further operated to receive the randomaccess message using a hybrid automatic repeat request entity.
 5. Themethod of claim 4, wherein the random access message is used forcollision resolution.
 6. The method of claim 4, wherein the base stationis further operated to receive the random access message using a sharedchannel.
 7. A base station comprising: a transmitter; a receiver; and aprocessor, wherein the processor: processes a random access procedurepreamble sequence received by the receiver from a wirelesstransmit/receive unit (WTRU); and causes the transmitter to transmit tothe WTRU, responsive to the received random access procedure preamblesequence, one or more signals identifying resources allocated forretransmission of a random access message by the WTRU to the basestation and indicating a number of times that the WTRU is to retransmitthe random access message to the base station, wherein the random accessmessage is different from the random access procedure preamble sequence,wherein the processor further causes the receiver to receive the randomaccess message using a hybrid automatic repeat request entity.
 8. Thebase station of claim 7, wherein the random access message is used forcollision resolution.
 9. The base station of claim 7, wherein theprocessor further causes the receiver to receive the random accessmessage over a shared channel.